Silicones are definitely controversial ingredients in cosmetic products. The misinformed reasons people suggest avoiding them include things like being unsafe for the environment, causing acne, interfering with other ingredients, being difficult to remove, providing no benefit and not being natural.
Of course, these concerns are mostly wrong and if you are focused on making the best performing products that you can, silicones are often your best ingredient choice. In this post we’ll look at silicones; what they are and why they are used in cosmetics. Other people have already explained why concerns about silicones are not supported by science.
What are silicones?
Silicones are compounds derived from the element Silicon which is the 14th on the periodic table of elements. It is located just below Carbon which means it will have some of the same chemical bonding characteristics of carbon. Like Carbon it has four positions in which it can form chemical bonds. Silanes are structurally similar to hydrocarbon alkanes and are a string of silicon atoms bonded (-Si-Si-) to each other and to hydrogens. These are much more reactive than organic alkanes and are rarely found naturally occurring.
Instead of silanes, most of the silicones you find in cosmetics are based on (-Si-O-Si-) bonds. They are produced by converting quartz into silicon then further reacting with methyl chloride which produces a variety of chlorosilanes. These are reacted further with water to produce silanols (-Si-OH) which can then be converted into things like Dimethicone, Cyclomethicone and all the other familiar silicones in cosmetic products.
Why are silicones used in cosmetics?
There are a number of reasons silicones are used in cosmetic products. These include
- Spreadability - Silicones have a lower surface tension then both oils and water which means the more easily spread on surfaces than those types of compounds.
- Feel - The low surface tension also makes silicones feel more slippery and lighter on the skin. This means they improve the feel of skin products. For hair products they can also the fibers feel less rough and more smooth.
- Slip - Still another consequence of the low surface tension is that silicones are great for detangling hair and making it easier to comb.
- Shine - Many silicones are not water soluble so they can leave a film on whatever surface they are applied. This property is useful for making hair look more shiny. It can also provide a shiny effect on skin when incorporated into makeup.
- Barrier - When used at a high enough level, silicones can create a barrier on skin which can protect it from chemical exposure and other environmental insults. This can also provide a great deal of moisturization through an occlusive action on skin.
- Foam reduction - When you want to create a cleanser that doesn’t produce a lot of foam, silicones are extremely useful.
What are the types of silicones in cosmetics?
The most basic silicones used in cosmetics include Cyclomethicone, Dimethicones, and Silanols (dimethiconol). Then there are derivatives of all these.
Cyclomethicone - This is a cyclic compound and the most commonly used types have either 4 silicon atoms (D4) or 5 silicon atoms (D5). These ingredients are volatile and evaporate more quickly than water and ethanol. This makes them great for inclusion in a product like an antiperspirant in which you want to have slip when applying it but don’t want to leave a film on the surface. It also works well in hair conditioners because it can provide slip on wet hair to make combing easier, but won’t build up.
Dimethicone - This is the general name for silicone polymers (-Si-O-) surrounded by methyl groups (-CH3). The characteristics of the material depends heavily on the average molecular weight of the polymer. Lower molecular weight dimethicone is more fluid and spreads more easily on surfaces. Higher molecular weight can be hard to spread and sticky like molasses. This is better for occlusion. Often a blend of silicones is used to get properties of both high and low molecular weight versions. Suppliers of silicone materials call these silicone fluids.
Silanols - When I learned about these they were called Dimethiconol which referred the fact that they had an -OH group as a side group on the polymer. This -OH group is reactive which makes silanols useful for creating other raw materials. But even as themselves, silanols can be used in cosmetic formulas primarily because they are water soluble. One of the biggest challenges of working with silicones is that they are not typically soluble in either water or oils. This means that silanols are excellent for leave-in hair conditioners. They can provide the shine, slip and feel of silicones, but will be easily washed out in future shampooings. It’s important to note that these materials won’t do much when put in a product that is meant to be rinsed off. They will just get rinsed away without providing much benefit.
Beyond these three types of silicone compounds, there are others including silicone esters, silicone surfactants, fluoro dimethicones, cationic silicones, silicone phosopholipids and more. But we’ll save talk of those for a future blog post.